Empirical orthogonal function analysis of winter sea surface temperature (SST)
anomalies over the Pacific domain (60°N-20°S) reveals an El
Niño-Southern Oscillation (ENSO) mode that is linked to the eastern
North Pacific, and a North Pacific mode that is linearly independent of ENSO.
The North Pacific mode exhibits maximum amplitude and variance explained along
~ 40°N, west of ~ 170°W. SSTs in this region have decreased by
~ 1.5°C from 1950 to 1987. The cooling in winter has been associated with
a strengthening of the overlying westerly winds.